From a148e33c42dd799c3b78acaf67305824f7797b5d Mon Sep 17 00:00:00 2001
From: Simon Goldschmidt <goldsimon@gmx.de>
Date: Tue, 18 Oct 2011 20:22:09 +0200
Subject: [PATCH] fixed default values of TCP_SNDLOWAT and TCP_SNDQUEUELOWAT
 for small windows (bug #34176 select after non-blocking send times out)

---
 CHANGELOG              | 4 ++++
 src/include/lwip/opt.h | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index ec814065..e97ed953 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -49,6 +49,10 @@ HISTORY
 
  ++ Bugfixes:
 
+  2011-10-18: Simon Goldschmidt
+  * opt.h: fixed default values of TCP_SNDLOWAT and TCP_SNDQUEUELOWAT for small
+    windows (bug #34176 select after non-blocking send times out)
+
   2011-10-18: Simon Goldschmidt
   * tcp_impl.h, tcp_out.c: fixed bug #34587: TCP_BUILD_MSS_OPTION doesn't
     consider netif->mtu, causes slow network
diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index 7f23dd45..48581e5a 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -978,7 +978,7 @@
  * TCP snd_buf for select to return writable (combined with TCP_SNDQUEUELOWAT).
  */
 #ifndef TCP_SNDLOWAT
-#define TCP_SNDLOWAT                    ((TCP_SND_BUF)/2)
+#define TCP_SNDLOWAT                    LWIP_MAX(((TCP_SND_BUF)/2), (2 * TCP_MSS) + 1)
 #endif
 
 /**
@@ -987,7 +987,7 @@
  * this number, select returns writable (combined with TCP_SNDLOWAT).
  */
 #ifndef TCP_SNDQUEUELOWAT
-#define TCP_SNDQUEUELOWAT               ((TCP_SND_QUEUELEN)/2)
+#define TCP_SNDQUEUELOWAT               LWIP_MAX(((TCP_SND_QUEUELEN)/2), 5)
 #endif
 
 /**